Field of the Invention
The present invention relates to the development of control units, such as are used in the automotive industry or in the aviation industry, for example, for controlling technical systems such as, e.g., engines or brakes. In particular, the present invention concerns testing devices that are used in the development process for the control unit.
Description of the Background Art
The development of control units has become a highly complex process. New control units and new control functions should thus be tested as early in the development process as possible in order to verify general functionality and to set the direction for further development. Towards the end of the development process, it is important to test the control unit, which has already undergone extensive development, as comprehensively as possible in order to make necessary modifications based on the test results before the control unit comes into use or enters mass production, so that it functions as desired under all conditions in later operation.
Three exemplary steps of the development process in which testing devices are used for testing the control unit are described below. So-called hardware-in-the-loop simulators (HIL simulators) are employed at a fairly late stage of the development process. Such HIL simulators contain a model of the technical system to be controlled, with the model being present in software. The HIL simulator may contain additional models as well, such as models of other systems that the technical system to be controlled interacts with. The HIL simulator also contains an input/output interface to which it is possible to connect the control unit, which has already undergone extensive development and is physically present as hardware. The functionality of the control unit can now be tested in various simulation passes, wherein it is possible to observe how the model of the technical system to be controlled reacts to the signals of the control unit, and how the control unit reacts to the events predefined by the model of the technical system to be controlled. In this process, it is possible to simulate not only normal operation, but also faults in the technical system to be controlled as well as faults in the control unit and faults in the communication between the control unit and the technical system to be controlled, such as, e.g., cable breaks or short circuits. Furthermore, it is also possible to observe the behavior of the technical system to be controlled together with the additional, interacting systems that are present as models in the HIL simulator.
In contrast, so-called rapid control prototyping (RCP) is a development step that takes place more toward the start of the development process. In RCP, the testing device is used in the role of the control unit. The testing device contains a model of the control unit to be tested. Because of the early stage of development, the model of the control unit to be tested is still fairly rudimentary in comparison to the later, final control unit. Nor is any hardware implementation of the control unit normally in existence yet; instead, the model of the control unit to be tested that is present in the testing device is a software model. Moreover, the testing device can contain additional models such as, e.g., models of technical systems that the control unit is later intended to interact with in addition to the system to be controlled. In this way, a broad environment of the control unit can be represented in the testing device. The testing device can be connected through an input/output interface to the technical system to be controlled itself, or to the control unit that exists to date for the technical system to be controlled. In the first case, there is a direct connection between the control unit to be tested, in the form of a software model, and the technical system to be controlled, which is physically present. In the second case, the control unit that exists to date is the technical system to be controlled by the RCP testing device. This control of the control unit that exists to date results in a modification of the control method of the control unit that exists to date, making it possible to test new control functionality via the externally connected RCP testing device. This arrangement is also referred to as bypassing.
In a still earlier phase of control unit development, the basic functionality of control and regulation methods can be evaluated in a purely computer-assisted manner. For this purpose, a model of the control unit can be connected to a model of the system to be controlled in order to test control functionality. The behavior of the model of the control unit can be observed and evaluated in interaction with the model of the later environment of the control unit. Once again, in addition to the model of the control unit and the model of the technical system to be controlled, there may be other models that represent additional elements of the environment of the control unit or of the technical system to be controlled, and that can be connected to the models of the control unit and of the technical system to be controlled for the simulation.
In the three phases of control unit development described, it is necessary, or it can be necessary or desirable, to connect models of different technical systems to one another in the testing device. Since one and the same testing device can be used for different simulations, the testing device is usually configured in a dedicated manner for each simulation or for each series of simulations. Accordingly, it is customary to produce particular connections between the models of different technical systems in the testing device prior to carrying out a particular simulation.
Nevertheless, there is as yet no satisfactory method that permits the connection of the models of technical systems in the testing device with acceptable effort while providing satisfactory adaptation to the individual case.